Olefin polymers films containing various types of additives are generally known in the art. One problem, however, observed in the films currently known is in achieving desired combinations of resin cost, polymer processability, film strength and film barrier ability. This problem is particularly acute in the area of films used for confinement of chemical treatment agents, and especially soil treatment tarpaulins or soil covering materials. For these and similar uses, large amounts of film are used to confine chemical treatment agents to the area where they are applied and are desired and expected to treat. The chemical treatment agents used, often very volatile gases, tend to diffuse, wash, dissolve or blow away unless prevented from doing so. The rapid loss or escape of these treating chemicals can be undesirable for several reasons. For example, (1) the chemicals may be hazardous or toxic in some way, (2) the desired treating effects may not be achieved, and/or (3) larger amounts of chemical may be required to achieve the desired effects. The problem of finding a film suitable for use as a chemical treating agent confinement film is further complicated by the fact that during usage such films are subjected to conditions and treated in a manner that punctures and tears in such films tend to occur.
The films currently used to confine chemical treatment agents and as soil treatment tarpaulins or soil covering materials are most commonly low density polyethylene films approximately one thousandth of an inch (1 mil) thick. Due primarily to their ability to resist puncturing and their ability to resist tear propagation should the film become punctured, these films are fairly well-suited for this usage. The main problem with these films, especially when used with volatile gaseous soil fumigation compounds such as methyl bromide (MeBr) and chloropicrin, is the permeation of the volatile gases through the film and out into the atmosphere. These soil fumigation substances escaping into the atmosphere, depending on their composition, can then present various types of environmental hazards. This loss of fumigant due to diffusion, unless prevented by using thicker, more expensive films, requires the application of larger doses of fumigant at a greater expense to ensure that a sufficient amount of the substance remains in the soil to achieve the desired soil treatment effects.
It is also known in the art that fatty acid amides can be added to olefin polymer films in small amounts (i.e., 0.5 percent by weight or less for non-filled films) as slip or anti-block agents making such films easier to handle and use. See, for example, U.S. Pat. Nos. 3,330,796; 3,645,822; 3,562,291; 2,770,608; 2,938,879 and 3,176,021.
It is an object of the present invention to provide novel olefin polymer films with improved barrier abilities, which films can be easily produced at low cost and are sufficiently resistant to puncturing. It is also an object of this invention to provide a method of confining a chemical treatment agent to areas of application and adjacent areas desired to be treated, which method uses for such confinement purposes olefin polymer films having good barrier abilities along with other desirable physical properties.